Lipoproteins. Flashcards
What is the problem of transporting lipids in the blood?
They are hydrophobic.
Where is albumin synthesised?
In the liver.
What can albumin transport in the blood?
Some free fatty acids and bilirubin.
How are lipids transported in albumin?
They are bound to hydrophobic pockets.
Is there anything albumin will not transport?
Free cholesterol.
TAGs.
Cholesteryl esters.
What is used to transport cholesteryl esters, TAGs and free cholesterol?
Lipoproteins.
What are lipoproteins?
Large spherical macromolecules.
What are lipoproteins made up of?
Lipids and specific proteins called apolipoproteins.
What is the structure of the outer shell of lipoproteins?
It is made from a phospholipid monolayer, free cholesterol and apolipoproteins.
What is special about the structure of apolipoproteins?
The outside is polar and it allows lipoproteins to be soluble in water.
What does the outer shell of an apolipoprotein surround?
A hydrophobic, neutral lipid core.
What will be placed in the core of an apolipoprotein?
Large amounts of TAGs and cholesteryl esters.
What are the 4 groups of lipoproteins?
Chylomicrons.
VLDL.
LDL.
HDL.
What fats do chylomicrons transport?
Exogenous fats from the diet.
What fats do VLDL transport?
Endogenous fats from the liver.
Where are chylomicrons released from?
By the intestinal mucosal cells.
What do chylomicrons carry?
Dietary lipids and lipid soluble vitamins.
What apolipoproteins are found in chylomicrons?
B-48, C2, E.
Where are VLDLs made?
In the liver.
What will VLDLs carry?
TAGs and cholesteryl esters that were formed by the liver.
How do VLDL molecules change when they are released into the blood?
They become IDL and eventually LDL.
What apolipoproteins make up VLDL?
B100, C2 and E.
Where are LDLs made?
In the blood from VLDL (via IDL).
What do LDLs transport?
They deliver cholesteryl esters to cells that need cholesterol for cell membranes.
What apolipoproteins make up LDL?
B100.
What is the job of HDLs?
They start off empty and travel to cells where they are filled with cholesteryl esters from the cell membranes of dead cells.
What apolipoproteins make up HDL?
C2 and E.
Which lipoproteins do reverse cholesterol transport?
HDL.
What is the order of density of the 4 lipoproteins?
High density lipoproteins (HDL).
Low density lipoproteins (LDL).
Intermediate density lipoproteins (IDL).
Very low density lipoproteins (VLDL).
Where is lipoprotein lipase found?
In the capillaries that are anchored close to the heart and fat cells.
What activates lipoprotein lipase (LPL)?
Apo C-II.
What is the job of LPL
To cleave TAGs in lipoproteins and to make free fatty acids from the leftover lipoproteins.
What happens to the free fatty acids that are cleaved by LPL in the heart?
They will go on to power the heart.
What happens in to the fatty acids that are cleaved by LPL in fat tissues?
They will be stored as fat for later use.
What apolipoprotein must be present to form chylomicrons?
APOB48.
What lipoproteins transport TAGs?
Chylomicrons and VLDL.
Will chylomicrons be found in the blood during fasting?
No.
What is a nascent chylomicron?
A full chylomicron.
What does a nascent chylomicron contain?
90% TAGS from dietary lipids.
5% lipid soluble vitamins.
5% cholesteryl esters.
How do chylomicrons enter the bloodstream?
Through a thoracic duct from the lymph system.
How is a chylomicron activated in the bloodstream?
When HDL removes 2 APLs.
LPL is activated by what transport proteins?
Chylomicrons.
If a patient has a deficiency in LPL, what will be the result?
High levels of chylomicrons in the blood.
What is necessary for the synthesis of VLDL?
Apo B-100.
What do VLDL molecules transport?
60% TAGs.
Cholesterol.
Cholesteryl esters.
What are classified as TAG rich lipoproteins?
VLDLs.
What does VLDL when it is released by the hepatocytes?
Only apo B-100.
How does VLDL become functional?
When HDL collides with this molecule it adds apo-C and apo-E.
What is the main purpose of VLDL?
To prevent TAG accumulation in the hepatocytes.
What is IDL?
The remnants of VLDL once TAGs have been cleaved from them.
What does LDL carry?
Around 8% TAGs and around 50% cholesteryl esters.
What is the main job of LDL?
To transport cholesteryl esters to cells that need cholesterol.
